Method for continuous extraction of liquid from a pasty suspension

ABSTRACT

A method for the continuous extraction of a liquid from a pasty suspension arranged in a layer on a support strip comprising elastically-deformable permeable zones separated by impermeable zones, the permeable zones putting into communication with each other the two faces of the strip are each subjected to a progressive contraction moving from the face in contact with the suspension towards the free face of the support. The compression pressure is obtained by passing the suspension-strip combination between press cylinders.

United States Patent Jacquelin Apr. 15, 1975 [5 METHOD FOR CONTINUOUS2,866,827 12/1958 Jurgeleit et a1. 210/400 ux EXTRACTION LIQUID FROM APASTY 2,881,127 4/1959 Hetzel 210/400 X 3,520,251 7/1970 Bodme 100/121 XSUSPENSION Inventor: Guy Jacquelin, Grenoble, France Assignee: CentreTechnique de lIndustrie des papiers, Cartons et Celluloses,Grenoble-Gare, Isere, France Filed: Sept. 20, 1971 Appl. No.: 182,239

Related U.S. Application Data Division of Ser. No. 47,037, June 17,1970, Pat. No. 3,669,011.

U.S. Cl. 100/37 Int. Cl. A47j 19/02; B30b 9/02 Field of Search 100/118,37, 121; 210/400,

210/401, 359, 386, DIG. 21

References Cited UNITED STATES PATENTS Fedeler, Jr 210/401 PrimaryExaminerPeter Feldman Attorney, Agent, or FirmChar1es E. Baxley, Esquire[57] ABSTRACT A method for the continuous extraction of a liquid from apasty suspension arranged in a layer on a support strip comprisingelastically-deformable permeable zones separated by impermeable zones,the permeable zones putting into communication with each other the twofaces of the strip are each subjected to a progressive contractionmoving from the face in contact with the suspension towards the freeface of the support. The compression pressure is obtained by passing thesuspension-strip combination between press cylinders.

4 Claims, 3 Drawing Figures v a i III/111112114 METHOD FOR CONTINUOUSEXTRACTION OF LIQUID FROM A PASTY SUSPENSION CROSS REFERENCE Thisapplication is a divisional application with respect to. my copendingapplication Ser. No. 47.037 filed June 17, 1970, now U.S. Pat. No.3,669,011.

The present invention relates to a method of continuous extraction of aliquid contained in a pasty suspension.

A conventional method of extraction consists of compressing, between thecylinders of a press, the pasty suspension arranged in a layer on apermeable support. If so desired, this suspension can be previouslythickened by filtration.

However, the proportion of liquid extracted from thepasty material bythis method is limited; in fact, the liquid extracted by continuouspressing in the compression zone of the cylinders flows back partiallytowards the upstream side and dilutes the suspension. This dilution mayin certain cases by developed to the point at which the continuity ofthe pasty layer is broken.

ln addition, the liquid absorbed by the permeable support is partlyrestored to the concentrated pasty material at the outlet of thecylinders, at the moment of release of pressure on the pasty layer. Thisdisadvantage. due to a suction effect by decompression has been limitedby certain devices comprising an under-fabric of synthetic material andrecesses which retain the absorbed liquid. These devices limit theeffect of suction by the layer during the compression, but they do notwholly eliminate this phenomenon.

The present invention is intended to obtain a systematic separation ofthe liquid expelled from the pasty layer by preventing its returnmovements at the outlet of the press. To this end, a method ofcontinuous extraction of a liquid contained in a pasty suspension,previously thickened by filtration if so required, consists ofcompressing between press cylinders, the suspension arranged in a layeron a permeable support. According to the invention, at the level of thepress cylinders, permeable and elastically-deformable zones aresubjected to a progressive contraction; these zones provided in thesupport between fluid-tight zones, put the two faces of the support intocommunication, the said contraction progressing in the centre of each ofthe permeable zones. from the face in contact with the suspension to thefree face of the support.

Thus, by compression of the pasty layer, the liquid is extracted fromthe suspension and is then absorbed by the permeable zones of thesupport; the progressive contraction of these zones tends to expel thisliquid towards the free face of the support at which it is collected.This transfer of liquid is irreversible, due to the progression of thecontraction which is effected from the face in contact with thesuspension to the free face. thereby preventing any return of liquid bysuction, to the pasty layer.

At a given moment, there exists in each permeable zone a depressionupstream of the contracted section, which is located downstream of thepress cylinders, namely in the part of the permeable zone located on thesuspension side, while an over-pressure exists downstream of thiscontracted section, which is located upstream of the press cylinders,namely in the part of the permeable zone located on the side of the freeface.

The upstream liquid is thus sucked towards the contracted section whilethe downstream liquid is expelled towards the free face of the support,in an irreversible manner.

The invention also relates to a flexible, endless support-strip intendedfor carrying the method described into effect. A strip according to theinvention comprises elastically-deformable permeable zones sepa rated byfluid-tight zones, the said permeable zones putting the two faces of thestrip into communication and being capable of having an obliquedirection with respect to the normal to the planes of these two faces.

The method of operation of a support-strip of this kind is as follows:The strip is caused to move parallel to its axis, and the active sidewhich supports the suspension layer passes between the press cylinders.Between the press cylinders, the permeable zones have an obliquedirection with respect to the normal to the planes of the two faces ofthe strip, either by their structure or by the effect of the action ofthe cylinders. The axis of these zones, orientated from the face incontact with the suspension towards the free face, forms an obtuse anglewith the direction of movement of the strip, orientated in the directionof forward movement.

When it passes between the cylinders, the assembly of the flexible stripand the suspension layer is compressed. Each oblique permeable zone issubjected to a contraction in its section located between the cylinders.Due to the forward movement of the strip and the obliquity previouslyreferred to, this contraction progresses through each permeable zonefrom the face in contact with the suspension to the free face. As hasalready been explained, the liquid expelled by the compression of thesuspension is thus irreversibly directed towards the free face of thestrip. The liquid downstream of the contracted section is expelledtowards this free face. while the upstream liquid is sucked towards thisface.

According to a first form of construction, the perm eable zones may beconstituted by a plurality of parallel channels, having an obliquedirection with respect to the normal to the planes of the two faces ofthe strip. The progressive contraction which passes along these channelsproduces an actual pumping effect on the liquid of the suspension.

According to other forms of construction, the strip 4 may be constitutedby a succession of inclined thin porous plates separated from each otherby thin inclined fluid-tight plates. It may also be formed by aplurality of small flexible tubes with a hollow core, suspended from athin flexible strip pierced with holes facing the core of the said smallflexible tubes. In the position of rest, these hollow-core tubes may beperpendicular to the faces of the strip, but at the moment of passinginto the press they take-up an inclined direction which is essential forcarrying the method described into effect.

Furthermore, for certain kinds of suspension, an intermediate filteringfabric may be provided between the suspension layer and thesupport-strip.

The description which follows below with reference to the accompanyingdrawings gives by way of nonlimitative example several forms ofembodiment of the invention. In these drawings:

FIG. 1 is a diagram intended to facilitate understanding of theprinciple of the method according to the invention;

FIGS. 2 and 3 are partial views in perspective of two support-stripsaccording to the invention.

An endless flexible strip of impermeable material. of which one side isshown at l in FIG. 1, comprises a plurality of oblique channels such as2, putting its two faces 3 and 4 into communication. The angle 01 shownin FIG. 1 between the axis of forward movement of the strip and thedirection of the channels is an obtuse angle. The upper face 3 of theworking side of the strip 1 carries a layer 5 of a pasty suspensionwhich has been thickened by prior filtration.

The strip 1, which is given a movement of translation (from right toleft in FIG. 1), is intended to pass be tween press cylinders 6 and 7which subject the strip and the layer 5 to a local compression. Meansshown diagrammatically at 8 for collecting the extracted liquid are alsoprovided underneath this strip 1.

The method of extraction of the liquid by means of this strip is asfollows: at a given moment, the orifices (suspension side) of certainchannels such as the channel 2a. reach the threshold of the zonecompressed by the cylinders. The liquid expelled from this compressedzone passes through these orifices and flows out into the channels 20.

A moment later. the orifices (suspension side) of these channels passbetween the cylinders and are subjected to a contraction due to thesecylinders (channels in the position of the channel 21)). The liquidcontained in these channels is driven in the direction of the arrowstowards the free face of the strip.

The contracted section then progresses in each of these channels towardsthe free face (channel 2c). The liquid located on the side of the face 4with respect to the contracted section is driven towards this face,while the liquid located on the side of the face 3 is sucked towards thecontracted section.

The orifice on the side of the face 4 finally reaches the zonecompressed by the cylinders (channel 211); it is thus subjected to acontraction which blocks it, thus preventing the liquid extracted frombeing sucked towards the face 3 by a suction effect caused by thedecompression of the suspension layer 5.

It will thus be understood that by this pumping effect directed from theface 3 towards the face 4, the transfer of liquid becomes irreversible.

In the particular form of construction shown in FIG. 2, the channels aresimply constituted by small tubes 9 with a hollow core, suspendedunderneath a thin flexible strip 10. in the position of rest. thesetubes 9 are perpendicular to the plane of the strip 10, but they take-upan oblique direction, similar to that of the channels 2, at the momentof passage between the press cylinders.

The support-strip shown in FIG. 3 is formed by a juxtaposition ofimpermeable oblique plates 11 and porous oblique plates 12. These plates12 may be formed from a pourous fabric.

It will of course be understood that the present invention is notlimited to the terms of the foregoing description, but comprises on thecontrary all the alternative forms within the scope of those skilled inthe art. The dimensions. angles. distribution of the channels thicknessof the strip. deformability. etc., are naturally adapted to the productsto be treated, to the speeds and other characteristics of the pressingaction.

In particular. in certain cases. it may be advantageous to add on thesurface an interposed filtering fabric so as to limit fouling of thestrip or to reduce its imprints on the material to be concentrated.

It is furthermore obviously possible to utilize at the same time twosimilar endless strips located on each side of the layer of material tobe treated.

What l claim is:

l. A process for extracting continuously liquid from a suspensioncontaining solids by means of a belt having two parallel faces and alengthwise dimension greater than its widthwise dimension; said beltbeing flat, flexible, deformable, liquid-tight and traversed in itsthickness by conduits which place its two faces in communicationpermitting passage of the liquid from one face to the other; in whichprocess:

a. a layer of the suspension is deposited on one of the faces of thesaid belt;

b. the belt, after the suspension is deposited as stated in step (a), isdeformed by applying to its entire width a force of compressionsubstantially perpendicular to its faces, thus effecting in the zone ofcompression a temporary obturation on a part of each conduit byconstriction of said conduit;

c. and causing the force of compression to advance in translation in thedirection of the length of the belt so that the conduits have, at leastat the place of the compression, an inclination with respect to theplane of the belt, and that their obturated portion is displaced fromthe end thereof in contact with the suspension layer to their oppositeend thus causing a pumping effect which transfers the liquid from thesuspension towards the opposite face'of the belt.

2. The process according to claim 1 in which the pumping is effectedalong conduits pierced obliquely in the deformable, flexible, solidbelt.

3. The process according to claim 1 in which the pumping is effectedalong conduits a portion of which protrudes beyond the face of the beltopposite the face in contact with the layer of suspension, thisprotruding portion placing itself in oblique position by flexing at thetime of its passage through the compression zone.

4. The process according to claim 1 in which the pumping is effectedacross conduits consisting of a porous material.

1. A PROCESS FOR EXTRACTING CONTINUOUSLY LIQUID FROM A SUSPENSIONCONTAINING SOLIDS BY MEANS OF A BELT HAVING TWO PARALLEL FACES AND ALENGTHWISE DIMENSION; GREATER THAN ITS WIDTHWISE DIMENSION; SAID BELTBEING FLAT, FLEXIBLE, DEFORMABLE, LIQUID TIGHT AND TRAVERSED IN ITSTHICKNESS BY CONDUITS WHICH PLACE ITS TWO FACES IN COMMUNICATIONPERMITTING PASSAGE OF THE LIQUID FROM ONE FACE TO THE OTHER; IN WHICHPROCESS: A. A LAYER OF THE SUSPENSION IS DEPOSITED ON ONE OF THE FACESOF THE SAID BELT; B. THE BELT, AFTER THE SUSPENSION IS DEPOSITED ASSTATED IN STEP (A), IS DEFORMED BY APPLYING TO ITS ENTIRE WIDTH A FORCEOF COMPRESSION SUBSTANTIALLY PERPENDICULAR TO ITS FACES, THUS EFFECTINGIN THE ZONE OF COMPRESSION A TEMPORARY OBTURATION ON A PART OF EACHCONDUIT BY CONSTRICTION OF SAID CONDUIT;
 2. The process according toclaim 1 in which the pumping is effected along conduits piercedobliquely in the deformable, flexible, solid belt.
 3. The processaccording to claim 1 in which the pumping is effected along conduits aportion of which protrudes beyond the face of the belt opposite the facein contact with the layer of suspension, this protruding portion placingitself in oblique position by flexing at the time of its passage throughthe compression zone.
 4. The process according to claim 1 in which thepumping is effected across conduits consisting of a porous material.